I can see this being interesting in traffic applications. Instead of the red/yellow/green traffic lights we have at intersections today, instead imagine a "laser counter" system that would "tag" various vehicles as they approached and would send a special signal to the car whose turn it was to go. The car, being self driving, would be integrated into all of this and then proceed, assuming the other cars follow the same contract. All it takes is one car to not understand the contract for this to be pretty scary though. Maybe the road could be tolled: the spike-track or barrier won't go down unless your car has proven that it can cooperate in the intersection protocol.